/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.startup;

import java.lang.reflect.Method;

import org.apache.catalina.Container;
import org.apache.tomcat.util.digester.Rule;
import org.xml.sax.Attributes;

/**
 * <p>
 * Rule that copies the <code>parentClassLoader</code> property from the
 * next-to-top item on the stack (which must be a <code>Container</code>) to
 * the top item on the stack (which must also be a <code>Container</code>).
 * </p>
 * 
 * @author Craig R. McClanahan
 * @version $Revision: 467222 $ $Date: 2006-10-24 11:17:11 +0800 (星期二, 24 十月
 *          2006) $
 */

public class CopyParentClassLoaderRule extends Rule {

	// ----------------------------------------------------------- Constructors

	/**
	 * Construct a new instance of this Rule.
	 */
	public CopyParentClassLoaderRule() {
	}

	// --------------------------------------------------------- Public Methods

	/**
	 * Handle the beginning of an XML element.
	 * 
	 * @param attributes
	 *            The attributes of this element
	 * 
	 * @exception Exception
	 *                if a processing error occurs
	 */
	public void begin(String namespace, String name, Attributes attributes)
			throws Exception {

		if (digester.getLogger().isDebugEnabled())
			digester.getLogger().debug("Copying parent class loader");
		Container child = (Container) digester.peek(0);
		Object parent = digester.peek(1);
		Method method = parent.getClass().getMethod("getParentClassLoader",
				new Class[0]);
		ClassLoader classLoader = (ClassLoader) method.invoke(parent,
				new Object[0]);
		child.setParentClassLoader(classLoader);

	}

}
